The building analogy works. If you're in a highrise, no elevator service is going to impact your business.

The back analogy works too. If you're an oil company, Goldman Sachs, AT&T or something similar, you have the bucks to pay someone for an empty emergency office complex for critical staff.

If you're anyone else, you're screwed when the elevators break/street floods/bridge falls down. That doesn't mean that buying a building or building a dam is a viable business continuity strategy.